Abstract:

The primary objective of this study is to study the effects of cable restrainers on the nonlinear seismic response of the San Gregorio Bridge. The computer program NEABS-86 was used in the nonlinear analyses.

The earthquake analyses focus on the relative displacements at the hinges, the restrainer stresses, and the abutment forces in both the longitudinal and the transverse directions of the bridge. The peak ground acceleration of the earthquake input, the seismic retrofit, the restrainer gap, and the hinge gap were varied. It was found that, in general, the cable restrainer system reduces the hinge responses in both the longitudinal and the transverse directions. Also found was that, when a zero restrainer gap is assumed, the hinge responses change significantly. It is recommended that the restrainer design be based on cases with both zero and non-zero restrainer gaps, to encompass all the critical forces, stresses and displacements.

Finally, some design methods for the longitudinal restrainer cable at intermediate hinges of the bridge were evaluated. A modified "Dynamic-Caltrans" design procedure was tested preliminarily, and showed some promising results (Abstract by authors).